Rubber composition and method of producing the same



Patented May 1,1928.

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This invention relates-t compositions of matter made from or containing rubber, and

more specifically to the treatment'of rubber with sulphuric acid and products so formed.

Heretofore, so far as I am aware, sulphuric acid has caused to react upon rubber only in such large proportion of the acid as to produce a hardftgranular, matevide inexpensive, tougb,-heat-plastic deriva tives of rubber suita Is for uses similar to those ofbalata and 'gutta-percha. A fur ther specific object is to provide materials of this character havinga low heat-softening point as compared with products heretofore obtained from the reaction of sulphuric acid on rubber. A still further obgect'is to provide an improved method of e acting a reaction between sulfuric acid and'rubber.

- I find that by mixin with rubber much smaller amounts of sulp 'uric acid than have heretofore been used, and heating the mixture, I am able to obtain a tough, highly heat-plastic product well suited for the manufacture of molded articles andothcr uses, the heat softening point being comparatively low.

By way ofexample, parts by weight of concentrated sul huric acid, specific gravity 1.84, are dilut with 1.25 parts 0 terial substantial y inert to the acid, such as fossil flour or titanium oxide. This aste is then milled into 100 parts by weig t of rurlber, keeping the mill rolls as ,cold as pos- 51 e. mary reaction of the acid and rubber, there by permitting theacid to be well disseminated in the rubber before the primary re-- action begins. The igment facilitates the handling of the ac-i and also hastens the mixingof the acid with the' rubber. The rubber is then sheeted out in sheets from $5 to 1 inch in thickness and heated'for to f hours at 125 C. to 130? C.

water and made into a aste with 2 parts of a ma- P The water serves to delay the pri- Application use January 11,1004. sum n. can.

u ct a hard, tough, thermo-plastic material which can be m'illed on a hot mill or .otherwise manipulated for such purposes as the impregnation of'fabric or the manufacture ofmo ded goods.

This thermo-plastic material is also char -acterized by itshigh dielectric strength and by its susceptibility of being .crushe at ordinary temperatures for molding of the crushed product, and of being re-milled at temperatures ra'n ing from to pounds steampressure; he material ma be mixed ewlth crude rubber or other p as'tics by milling, or may be compounded with fillers,

pigments or colors.

- A product having similar characteristics is obtained by the use of as hi h as 25 parts -of acid in accordance with t e above example, but when,su ch high proportion of am 1s -used I prefer to use a larger proportion .of plgment to acid, to permit 'the ar amount of acid to be taken u by the rub r before the primary reaction as substantially advance By using still smaller amountsof .sul-- phuric acid than that set out in the above example, I am able to obtain a product similar in many res ts to soft rubber vulcanamsle, 2 to 3 parts of concentrated sulphuric aci properly mixed with ,5 of. its weight ,of fossil-flour brother inert pigment is mixed into parts by weight of rubber on, a. mill. 7

heated forabouts 20 hours at C. in an oven, in a mold, or by other suitable means. The resulting product is resilient under compression, somewhat elastic, and in general resembles soft vulcanized rubber.

I desire it'to be understood that the exression concentrated sulphuric acid, as used hereinbefore-i-in this specification an also in the ap izedby theuse of sulphur. By way of 'ex- The rubber so treated is. then pended claims, is intended only I to define the proportion of active ingredient in the acid, and not as defining the concentrat1on of the'acid as used,

' My invention is subject to cedure orto the exact'proportions desen I claim-:- I 1. The method of producing a rubber composition which' comprieesmixing through a of rubber a-relatusly small quantity L modification t d ggltmgfrom its sec ,and 'I do not wholly: it my to e exact ro- -mixture to a reaction tempe .position which comprises e ectin of sulfuric acid, and heating the mixture to 'a reaction tern rature.

2. The method of producing a rubber composition which comprises mixmg into a mam of rubber sulfuric acid in. amounts not substantially greater than the acid equivalent of 25 parts by weight of concentrated sulfuric acid gr. 1.84) to 100 parts by weight of rubber, and heating the resulting rature. 3. The method 'of producing a rubber composition which comprises dispersingthrough -'a mass of rubber sulfuric acid in amounts ranging between the acid equivalent of from 2 to 25 by weight of concentrated sulfuric acid (5 gr. 1.84) to 100 parts by weight of rub r, and heating the'resulting mixture to a reaction tem rature.

.4. The method of producln a rubber co man Intimate mixture of sulfuric acid an rubber, in the absence of a solvent of rubber, and so heating the man as to form a tough hesive, heat-Elastic, solid reactibn 5. The met 0d of producing a rubber composition which comprises mixing sulfuric acid with a solid constituting a carrier, millthe resulting mixture into a mass of reaction temperature.

In rubber, and heating the resulting mass to a of heat of sulfuric acid mixture into upon heating ofthe resultant mass, a tough,

cohesive, reaction product, and heating sal resultant m'ass.

8. As a new composition of matter, the product-of the reaction, in the absence of a solvent, of sulfuric acid and rubber in pro-- )ortion of the acid 7 uivalent of from 2 to 5 rts'hy weight 0 concentrated sulfuric acid (sp. gr. 1.84) to 100 parts of rubber.

9. As a new com 'tion of matter, 'theproduct'of the reaction under the influence dispersed through a mass of rubber in the pro I of 100 rts by weight of rubber to acid equ vaent of from between 2 to 25- weight of concentrated sulfuric aci (sp. gr. 1.84).

. In 'witneswhereof I have hereunto set my hand this 11th day of Ja'nuarfl HABRY- 1924. I FISflEB. 

